textproduct: Rapid City

KEY MESSAGES

- Showers and thunderstorms through Friday. Highest rainfall amounts of 1/2" to an inch over northwestern South Dakota and the northern Black Hills.

- Mild Saturday. Chance of afternoon showers and thunderstorms over the Black Hills.

- Warmer beginning on Sunday and continuing through next week.

DISCUSSION

(This Evening Through Thursday) Issued at 1248 PM MDT Thu May 21 2026

Upper level analysis has an area of low pressure centered over western Saskatchewan and a trough extending down the east side of the Rockies to the Four-Corners area. At the surface, a stationary boundary extends through the western Dakotas into southeastern Wyoming. Showers and thunderstorms have already begun to pop over the northern Black Hills, and expect coverage to increase this afternoon along the frontal boundary as the upper level trough moves toward the forecast area. CAPE is around 500 J/kg, thus a few stronger storms capable of producing gusty winds and hail are possible this afternoon.

Expect showers/isolated thunderstorms to overspread the entire forecast area tonight before ending from west to east on Friday. Lower end/25th percentile precipitation accums are 0.1" to 0.2" across northeastern Wyoming and southwestern South Dakota upward to 3/4" to an inch across northwestern South Dakota and the northern Black Hills. Higher end/75th percentile are up to 1.75" across northwestern South Dakota.

As the system moves out on Friday, breezy northwest winds are expected, especially across the South Dakota Plains where gusts around 45 mph are possible for a few hours late Friday morning. Sustained winds should average around 25 mph. With winds on the low end of advisory criteria, have decided against any wind highlights at this time.

Temperatures on Saturday will begin to warm up, with highs in the mid 60s to mid 70s. Residual cold pool aloft and lingering low-level moisture could support isolated showers over the Black Hills in the afternoon.

The warming trend begins on Sunday as the western upper ridge builds. Above normal highs in the mid 70s to upper 80s will return with even warmer conditions on Memorial Day. The upper flow turns more south-southwesterly on Tuesday and the area remains in south- southwesterly flow through the end of the week. This will likely allow for moisture to advect into the area and could be the start of the severe weather season - which is typical for this time of year.

AVIATION

(For the 18Z TAFS Through 18Z Friday) Issued At 1136 AM MDT Thu May 21 2026

A cold front is moving through the region today, bringing thunderstorm chances and gusty northerly winds behind it.

A disturbance moving over the area has combined with the cold front to produce showers over northeastern WY. Thunderstorms have already popped up over the northern Black Hills and these will continue to develop through the afternoon/early evening, then rain for the rest of the forecast period.

Some snow will occur over the higher elevations of the Black Hills. The result will be MVFR/IFR conditions slowly moving from northeastern WY into the Black Hills later today. But tonight, widespread MVFR/IFR conditions will develop over western SD with local LIFR conditions over the Black Hills.

Improving weather conditions likely after 12z as the rainy/cloudy weather moves eastward.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.